Question

If onion has 16 chromosomes and 2C DNA content in its each cell, then during mitosis at G1, S, Prophase and Anaphase, the number of chromosomes and DNA content will be:-

Options:-
[Written in order of G1, S, Prophase, Anaphase. First no. of chromosomes, then DNA content]
A)16, 2C; 16, 2C; 16, 4C; 32, 4C
B) 16, 2C; 16, 4C; 16, 4C; 32, 4C
C) 16, 4C; 16, 2C; 16, 2C; 16, 4C
D) 16, 2C; 32, 4C; 32, 4C; 32, 4C​

Answer 1

Answer:

In S phase the amount of DNA gets doubled due to relocation process and chromosomes number of chromosomes also gets doubled but the chromosome is unable to separate due to which chromosome pair is considered as 1 in the phase at anaphase stage the chromosomes get separated and becomes 32 from 16.

Hence in G1 phase=16 chromosomes and 2C

In S phase = 16 chromosomes and 4C

In M phase =32 chromosomes and 4C

Answer 2

Initially the cell has 16 chromosomes and 2C DNA content.

• In G1 Phase, even though cell is metabolically active there are negligible changes taking place at the genome level. Thus, chromosome number and dna content remain conserved. [Option (c) is eliminated]

• However during S phase, process of dna replication begins and the ploidy of the cell is doubled. Chromosome number remains the same. For in.stance, 2C dna content becomes 4C. [Option (a) and (d) are eliminated]

Option (b) is correct.